1. Field of the Invention
This invention relates generally to orthodontic appliances, and more particularly concerns an orthodontic bracket allowing ligature ties to be placed on the orthodontic bracket so as to control the friction between an archwire and the bracket.
2. Description of Related Art
Orthodontic appliances, such as brackets, buccal tubes and the like, are typically applied to teeth by adhering the appliances to the surface of the teeth to orient the teeth by the application of forces on the teeth by such orthodontic appliances. Such appliances typically include archwire portions for receiving an archwire and ligature elastic bands to provide corrective forces to straighten and reposition the teeth. The orthodontic appliances include a base portion adapted to conform to the shape of the teeth to which they are applied, and elastic or wire ligature ties are used to hold the archwire in the archwire slot during initial and intermediate stages of treatment. However, tooth movement and straightening can be slowed by friction caused by such elastic or wire ligature ties, increasing the duration of orthodontic treatment. It is thus desirable for such ligature ties to remain above the archwire particularly during such initial and intermediate stages of treatment when the most significant amount of movement and straightening of teeth typically occurs, in order to allow the archwire to slide freely with minimal friction when such movement is necessary to facilitate tooth movement and straightening.
One known orthodontic bracket provides a base, a pair of opposing tie wings including a gingivally extending tie wing and an occlusally extending tie wing, an archwire slot defined in a vertical element between the pair of opposing tie wings, and a hook having a ball portion adapted to be oriented to extend toward the gingival side. A horizontal element is connected to the vertical element and includes opposing first and second ends extending away from the vertical element defining a pair of spaced-apart wire engaging points engageable with the arch wire for enabling rotational control of the bracket during use. The ends of the horizontal member also define horizontally extending wings for engaging stretched elastomeric modules to enhance rotational control. The slot in the vertical element has its lower surface vertically spaced from the horizontal element to limit contact between the arch wire and the horizontal element.
Another known type of orthodontic appliance provides for a bracket having one or two pairs of opposing gingival/occlusal tie-wings projecting on either side of an archwire slot, with gingival/occlusal hooks. The bracket includes four shoulders on the free ends of the bracket, with two shoulders being located on opposite sides of the archwire slot with respect to each other on the mesial end of the appliance, and the other two shoulders being located on opposite sides of the archwire slot with respect to each other on the distal end of the appliance. Each shoulder is adapted to support a ligature spaced apart from the archwire in the archwire slot to permit the appliance to move relative to the archwire during orthodontic treatment.
Another type of orthodontic appliance provides for a bracket having a pair of opposing T-shaped tie wings, with an archwire slot between the tie wings. Notches are provided on each of the mesial and distal sides of a center leg of each of the T-shaped tie wings for receiving a ligating device. A T-shaped hook may also be provided as an extension to the center leg of one of the T-shaped wings, to facilitate retention of a traction device. The tie wings include ligating support notches having a sloped portion extending toward the slot extending from the gingival or occlusal periphery of the tie wing, and having a curvilinear, concave configuration to reduce frictional engagement between an archwire positioned in the slot and a ligating device positioned across the archwire slot. The archwire slot may also include convex sidewall and/or floor portions to reduce frictional engagement between the archwire and bracket. However, it would be desirable to provide an orthodontic appliance that also allows full contact of the ligature ties and archwire when desired, such as in the finishing stages of treatment. It would also be desirable to provide the orthodontic appliance with additional features to assist the doctor in orienting the orthodontic appliance to its optimal position, and to allow the ligature to be placed spaced apart from or next to the archwire depending on the friction desired. The present invention meets these and other needs.
Briefly, and in general terms, the present invention provides for an orthodontic bracket that permits a ligature tie to be placed on the orthodontic bracket spaced apart from an archwire for the bracket to allow the archwire to slide freely with respect to the orthodontic bracket with minimal friction, and that permits a ligature tie to be placed on the orthodontic bracket with full contact between the ligature tie and archwire, as desired. The orthodontic bracket also includes features to assist an orthodontist in orienting the orthodontic appliance to an optimal position, and to allow the orthodontist the options of placing the ligature tie in different positions depending on the desired degree of friction between the ligature tie and the archwire.
The present invention accordingly provides for an orthodontic bracket having a body comprising a plurality of tiewings, and a plurality of posts extending in the mesial/distal direction. In a presently preferred embodiment, the plurality of tiewings are located on the occlusal side of the orthodontic bracket, and in one presently preferred aspect, may also include a center post between the tiewings, for placement reference and ligation of the orthodontic bracket. In a presently preferred aspect, a hook may be provided on the gingival side of the orthodontic bracket for anchorage and ligating of the orthodontic bracket. In another presently preferred embodiment, tiewings may be provided on the occlusal and gingival side of the orthodontic bracket. The plurality of posts extending in the mesial/distal direction may be provided on the gingival side, or on the occlusal and gingival sides of the orthodontic bracket, to assist in bracket placement and to direct an elastomeric or wire ligature over or under an archwire occupying the archwire slot during treatment, as desired. The bracket is preferably comprised of cobalt chromium alloy, or may alternatively be comprised of another suitable biocompatible alloy.
In another presently preferred aspect of the invention the bonding base of the orthodontic bracket may be formed to have a molded recessed number for identification of the tooth location for the orthodontic bracket. In another presently preferred aspect, a biocompatible wire clip ligature, or a biocompatible cap ligature, may be provided to fit over the orthodontic bracket to serve as a ligature to retain an archwire in the archwire slot of the orthodontic bracket.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.